DIY audio cable

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  #1  
Old 05-24-14, 12:58 AM
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DIY audio cable

Hey guys,

Im trying to make a cable to record direct line in into the GoPro Hero3+. I have bought the USB external mic cable. Heres the run down

Im doing my private pilots license and want to record my flight on my gopro. I want to record all audio between my instructor and myself and air traffic control.

The deal is, there are two plugs in the cockpit. One for audio out do I can hear all ATC (air traffic control) audio and the second is the MIC input so I can speak to the pilot and ATC.

What I want to do is integrate the two into a single mic input into the GoPro external MIC input. So I can hear all ATC audio, my own audio and the instructor audio.

I am thinking about just connecting the microphone in parallel with the audio (both mono) and then all audio will just emulate over the the mic input.

Heres a diagram of what I mean.

[image]Untitled-1.fw.jpg[/image]

Thats just the input, would I be right just putting it all in parellel?

Appreciate any help, im halfway done with the cable!

Cheers
 
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Old 05-24-14, 06:47 AM
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That won't work because the mic level is not as high as the level from the cockpit (ATC) audio. Also, the cockpit audio will be very loud and distorted in the headsets because it will be back-fed into the mic lines.

It would be better if you could tap the headset earcup audio since it has both ATC and internal mics. If it is the type that has separate 1/4" (6.5mm) jacks for mic & ears, use a simple y-cord to split the feed and an adapter cable between the y-cord and GoPro.

If it has a single connector, two of the pins should carry earcup audio.

Sample of a Y Cable

Sample of an adapter cable, assuming you bought the GoPro 3.5mm Mic Adapter.
 
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Old 05-24-14, 08:34 PM
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It's been a long time since I've been in a Cessna.. Is there 'talkback' to your own earpieces from your mic (as in can you hear yourself talk through your own earpieces)? If there is, it should work the way Rick said. If not then by tapping the earpiece signal you'd get ATC and your instructor, but not yourself.

A low tech way would be to just get a scanner or radio that has the air band and put it near the GoPro to pick up ATC.. It should pick up your conversation with your instructor fairly well on its own..
 
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Old 05-25-14, 12:24 AM
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Thanks for the replys guys!

I hear what your saying, but again like Matt says, I would imagine there would need to be feedback of me talking through my own headphones or all my talking will not be recorded.

Its really annoying that they have split the Audio and MIC outputs like that in this plane, Im flying a robin, and im sure most planes are just a single 6.5mm 4prong plug with both audio and mic on the single plug (duh)

So my only option here is to basicly try to capture the AUDIO channel?

So I would basicly just tap into the audio output (in parallel)? Hoping this captures my own audio of me speaking etc.

There are a few cables online that are made this specifically, but none of them have separate channels for mic and audio (because that seems like a dump idea to separate them on separate plugs).

Cheers
 
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Old 05-25-14, 06:09 AM
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Most common in GA fixed wing aircraft are the two separate plugs so get used to it. It's an antiquated system but it's the standard. Helicopters commonly use a single plug with four contacts. Here is a page that describes what is used most commonly in each class of aircraft.

You must be in Europe? There are not many Robin in North America.

Also, do a search online for "aircraft audio adapter" or "aircraft gopro adapter". Cables already exist that plug into the aircraft's headset plugs and provide an output for a GoPro. Here is one but I'm sure you can find a supplier in Europe if that's where you are located.

 
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Old 05-25-14, 06:51 AM
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Again, the reason the mic and headset cables cannot be simply combined in parallel is because of the significant difference in levels. A microphone needs an amplifier, and the headset signal is already amplified.
 
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Old 05-29-14, 06:32 AM
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Get a mixing preamp with a mic input for your microphone and a "line" or "aux" input for the air traffic control audio. This will let you adjust the levels of both signals to get a pleasing result.

Does your Gopro amp have a line input or aux input? You may not feed a typical preamp output directly into the mic input of the next piece of equipment; that will cause an overload with distortion and in extreme cases fry the mic input. While you might think of turning the master volume of the mixing preamp way down, there will be some hiss or hum in the output that will be obtrusive.

You could construct a level reducer (attenuator) using a potentiometer to allow the preamp output, hiss and all, to be scaled down to go into a mic input of the next piece of equipment.

Another possibility is to get a microphone only preamp and use a Y connector to parallel the preamp output and the ATC output into a line input of the Gopro. This is not guaranteed to work; it depends on how the electronics prior to the ATC output and the electronics inside the microphone preamp are designed.
 
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